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DESIGNATIONS
CAS No.: 7440-38-2
Registry name: Arsenic
Chemical name: Arsenic
Synonyms, Trade names: Grey arsenic, metallic arsenic
Chemical name (German): Arsen
Chemical name (French): Arsenic
Appearance: bright silver-grey metal, brittle and of average hardness;
other modifications: yellow (unstable), black
BASIC CHEMICAL AND PHYSICAL DATA
| Chemical symbol: | As |
| Rel. atomic mass: | 74.92 g |
| Density: | 5.72 g/cm3 |
| Boiling point: | 613°C (subl.) |
| Melting point: | 817°C (at 3.7 MPa) |
| Vapour pressure: | 0 Pa |
| Solvolysis/solubility: | in water: very low |
BASIC DATA ON SELECTED COMPOUNDS
| CAS No: | 1327-53-3 | 7784-42-1 |
| Chemical name: | Arsenic trioxide | Arsine |
| Synonyms, Trade names: | White arsenic | |
| Chemical name (German): | Arsentrioxid, Weißarsenik, Arsenik | Arsin, Arsenwasserstoff |
| Chemical name (French): | Arsenic | Arsine, hydrure d'arsenic |
| Appearance: | white powder or small white pieces, odourless | colourless gas with garlic-like odour |
| Empirical formula: | As2O3 | AsH3 |
| Rel. molecular mass: | 197.82 g | 77.95 g |
| Density: | 3.7-3.87 g/cm3 | 3.48 g/l |
| Relative gas density: | 2.7 | |
| Boiling point: | -55°C | |
| Melting point: | 200°C (subl.) | -117°C |
| Solvolysis/solubility: | in water: 18 g/l | in water: 20 vol.% |
| Conversion factors: | 1 ppm = 0.12 mg/m3 1 mg/m3 = 8.22 ppm |
1 ppm = 0.31 mg/m3 1 mg/m3 = 3.24 ppm |
ORIGIN AND USE
Usage:
The demand for metallic arsenic is limited. Arsenic is used
in nonferrous alloys (e.g. to enhance the temper of lead-alloys)
and highly pure arsenic is needed to produce GaAs- and
InAs-semiconductors.
With the introduction of antibiotics, pharmaceutical products
containing arsenic have become less important. Moreover, arsenic
compounds have been used as pesticides (prohibited in Germany)
and in the production of pigments.
Origin/derivation:
Arsenic is an element. The average arsenic content of the
earth's crust has been estimated at 5 x 10-4 %.
It is mainly obtained from complex ores. France, the former USSR,
Sweden and Mexico are the main arsenic producing countries.
Production figures:
Arsenic production in tons of As2O3
content per year (1978)
| France | 7280 |
| USSR | 7640 |
| Sweden | 6706 |
| Mexico | 6263 |
| World | 40283 |
(figures taken from ULLMANN 1985)
Toxicity
| Humans: | LDLo 1 mg/kg, oral (arsenic trioxide) | acc. Koch 1989 |
| TCLo 0.5 ppm, inhalation (arsine) | acc. Koch 1989 | |
| LD 50 mg/m3, inhalation (arsine) | acc. Koch 1989 | |
| Mammals: | ||
| Rat | LD50 4.5 mg/kg, oral ( arsenic trioxide) | acc. Koch 1989 |
| Mouse | LD50 43 mg/kg, oral ( arsenic trioxide) | acc. Koch 1989 |
| Rabbit | LDLo 4.5 mg/kg, oral ( arsenic trioxide) | acc. Koch 1989 |
| Aquatic organisms: | ||
| Fish | LC50 10-100 mg/l (96h), arsenic trioxide | acc. Koch 1989 |
Characteristic effects:
Humans/mammals: Pure arsenic is not toxic, but contaminations of technical arsenic (e.g. with As2O3) have to be considered. Acute poisoning mostly occurs by ingestion and inhalation of inorganic trivalent compounds such as As2O3. Symptoms are strong gastrointestinal disturbances, cramps and circulatory collapse. Airborne dusts often result in irritation of exposed skin and mucous membranes. Chronic poisoning can be caused by the intake of food and water with arsenicals or by inhalation of airborne dusts during long-term occupational exposure. Symptoms may appear even after many years of latency. Chronic poisoning results in damage to bone marrow, blood, liver, respiratory tract and central nervous system.
Acute poisoning with arsine results in retarded but rapid hemolytic anemia.
ENVIRONMENTAL BEHAVIOUR
In aquatic systems, arsenic mainly exists in the form of arsenides and arsenates. In sediments and soils, arsenates are readily absorbed at iron or aluminium hydroxides thus reducing their percolative abilities and speed as well as their availability for biological systems. In aquatic phases, arsenic forms insoluble precipitates with a number of compounds (Ca,S,Ba,Al,Fe) resulting in the elimination of arsenic compounds from the water. In microorganisms, plants and animals, methylation and reduction of arsenic compounds take place. Thus, a number of chemophysically and biologically stable arsenic compounds are produced [KOCH 1989].
Half-life:
The average biological half-life is about 60 days
(rats/rabbits) due to the accumulation of arsenic in the
erythrocytes. For humans, half-life is shorter because of a fast
excretion of arsenic [KOCH 1989].
ENVIRONMENTAL STANDARDS
Medium/ acceptor |
Sector |
Country/ organ. |
Status |
Value |
Cat. |
Remarks |
Source |
| Air: | Emiss. | D | L |
0.2 mg/m3 | mass flow > 5 g/h2) | acc. TA Luft, 1986 | |
| Workp | D | L |
0.1 mg/m3 | TRK | oxides, acids and their salts | acc. AUER Technikum 1988 | |
| Workp | D | L |
0.2 mg/m3 | MAK | arsine | acc. AUER Technikum 1988 | |
| Workp | USA | (L) |
1) | TWA | oxides | acc. AUER Technikum 1988 | |
| Workp | USA | (L) |
0.2 mg/m3 | TWA | arsine | acc. AUER Technikum 1988 | |
| Workp | SU | (L) |
0.3 mg/m3 | oxides | acc. AUER Technikum 1988 | ||
| Workp | SU | (L) |
0.3 mg/m3 | arsine | acc. AUER Technikum 1988 |
1) suspected human carcinogens
2) dustlike As and its compounds, stated as As
ASSESSMENT/COMMENTS
The toxicity of arsenic compounds differs significantly. Anorganic compounds are generally more toxic than organic ones. Some arsenic compounds are even carcinogenic. It is particularly significant as a workplace poison.